Method for making white and bleached wood pulp suitable for the manufacture of paper without addition of cellulose



June 23, 1931.

v HETHOD FOR MAKING THE EANUFACTURE OF PAPER WITHOUT ADDITION E. ELGERUS 3,811,783 WHITE AND BLEAGHED WOOD PULP SUITABLE FOR 0? CELLULOSE Filed Batch 28, 1929 Patented June 23, 1931 l,&ll,783

ERNST ELGERUS, OF NIKLASDORF-ON-THE-BIUR, AUSTRIA IlIE'II-IOD FOR MAKING 'W'HITE AND BLEACHED W'OOD EULP SUITABLE FOR THE IMAHIL FACTUR-E OF TRAPER VIITHO'UT ADDITION OI CELLULGSE Application filed March 28, 1929, Serial No. 350,778, and in Germany September 26, 1927.

This invention relates to a method for making white and bleached wood pulp suitable for the manufacture of paper without addition of cellulose.

Quite a number of methods have been proposed for utilizing the waste sulfite liquor, coming from the. boilers in the manufacture of sultite pulp. According to one of these methods the waste sulfite liquor is used for treating disintegrated wood in a pressure boiler, into which steam of five atmospheres pressure is introduced, thus boiling the wood in the waste sulfitc liquor at a temperature of about 128 C. After a treatment of about 3 to 4 ho rs the decomposed wood is separated into fibres in an edge mill: the. disintegrated material may directly be used for the manufacture of wrapping paper and the like.

According to the invention the hot waste suhite. liquor coming from the boilers in the manufacture of sulfite pulp is utilized in a more economical manner than that described above for decomposing wood for the manufa ture of wood pulp. which can be used for making paper without addition of cellulose. I have namely found, that excellent results in decomposing wood with waste sulfite liquor for the purpose described are also obtained, when the hot waste sulfit-e liquor is acting upon wood without any further supply of heat such as introducing steam into the pressure vessel containing the wood to be treated and the waste sultite liquor. It has been found that, in order to utilize completely the heat contentof the hot waste liquor so that the residual SO contentwill exertthe desired disintegrating and bleaching effect on the wood, it is only necessary to produce a certain pressure in the vessel, for example 3 atmospheres or more. This can be efiect-ed, for instance, by pumping into the vessel so much of the hot waste liquor that the desired pressure is attained-and thereafter leaving the wood, without any further supply of heat to the action of the hot liquor under the pressure thus attained for several hours for example three hours. or the desired amount of the hot waste liquor may be pumped into the treating vessel charged with wood and air or other suitable gas pumped in with a compressor until the desired pressure is attained, the wood being then left to the action of the liquor for the necessary length of time without any further supply of heat. The decomposition of the wood treated in this way is in about three hours carried so far. that it can be disintegrated in an edge mill to s ghtly yellowish wood pulp suitable for making paper without addition of cellulose. If the time of treating the wood in the described manner is increased or the pressure during treatment raised to pressures ab to three atmospheres the deconuvosition of the wood is carried so far. that nearly white wooe pulp with good mechanical properties is obtained.

The described process ma possible the full utilization of the heat- SO content of the waste liquor for the. production of a product. which on mechan cal 'isintegration gives a long-fibered white ground pulp, from 19 which a printing paper may be made on a paper machine running at 150 meters speed without the addition of cellulose. The power consumption for the grinding of the. wood treated by the presentprocess only about one-half that used in the usual grinding process.

The annexed drawings show by way of es;- ample and schematically two small plants for carrying out the invent.

.ccori;ling to the scheme in 1 of the drawings the hot waste sulfite liquor in the. sullite boiler drawn o by a pump 4 when the sulfite boiling is fin? need and pumped into the pressure vessel 1. which has prcs yiously been filled with wood on a carriage 2. The pumpingof hot. waste sullite liquor int-o the pressure vessel 1, is continued until a suitable superatmospheric .ure such three atmospheres is obtained in the pressure as vessel 1. Then the wood allowed to stand without further supply of heat under superatmosuheric pressure in the waste suliite liquor for several. say four hon If necessary compressed air may he messed into the pressure vessel 1. during the treatment. hen the treatment finish-2d the waste sulfite liquor is drawn oil. the decomposed -ood removed from the pressure vessel and disintegrated to pulp in an edge mill or the like.

The scheme shown in Fig. 2 of the drawings ditiers from the above scheme only by the fact, that the pressure vessel 1 is vertical instead of horizontal.

Instead of wood one can also treat in the m.- manner the t'llllliPiD-QS obtained by the decorrication of wooden stems.

I claim:

1. A method for making bleached wood pulp which co :t: in treating wood for several hours at superatmosoheric pressure with hot waste sulhte l' uor without supplying an h art other than that contained in the liqu-t and d sintegrating the treat-ed wood to mechanical vood pulp.

31 method for making bleached wood which consists in pumping hot waste re liquor into a closed vessel filled with wood until LlpHtitll'lOSPllQllC pressure is ob- Lined in the vessel. keeping the. superatmosphericv pressure in the vessel for several hours without supplying an l eat other than that co""ained in the liquor and releasing the pressure in the vess l. relno 'ing the wood n the vessel and chsintegmting the treat reod to mec anical wood pulp.

making bleached wood in pumping hot waste e o a deed vessel filled with until supcratmo pheric pressure of at Tee annosphcrcs is obtained in the vessel. keeping the 'superatmospherie pressure in the vt 1 for several hours without suppl -iing :11 Y neat other than thatcontained in the liquor and releasing the pressure in the vessel. removing the wood from the vessel nil-d disintegrating the treated wood to mechanical wood pulp.

l. A method for making bleached wood *ulp which consists in pumping hotwaste lite liquor into a closed vessel filled with wood. introducing compressed air into the vessel until superatinospheric pressure is obtained in the vessel, keeping the superatlnospheric pressure in the vessel for several hours without supplying an ieat other than that ined in the liquor and releasing the pressure in the vessel, removing the wood from the vessel and disintegrating the treated wood to mechanical wood pulp.

In testimony whereof I ailix my signature.

ERNST ELGER-US. 

